It is desirable to minimize loss of tomato tissue, that is tissue from the body of a tomato, when separating the skins from the tomatoes. A common device for heat treating tomatoes to separate their skins is a steam peeler, which is a pressurized chamber of hot, saturated steam through which tomatoes are conveyed for a relatively short period of time to heat their skins, which causes the skin material to break away from the tomato body. After the steam peeler, the tomatoes move through scrubbers, which physically remove the skins. The assignee of the application herein, FMC Corporation of Madera, Calif., USA, manufactures a steam peeler apparatus, Model SP-20, which is a complete tomato peeler system in which the present invention is designed for use. FMC's brochure "SP-20 STEAM PEELER SYSTEM" describes the peeling process in more detail and is incorporated herein by reference.
It is known that subjecting tomatoes to a two-stage heating process reduces loss of tomato tissue during peeling due to a reduction in breakdown of skin cell structure. Two-stage heating has a minimum effect on inner mesocarp cells of tomatoes, and results in localized breakdown of the first couple layers of skin cells. An article "Microstructure of Steam Peeling", Journal of Food Science, Vol. 53, No. 3, 1988, discusses in more detail the science and advantages of two-stage heating. This article is also incorporated herein by reference.
U.S. Pat. No. 5,862,812 of Dahl et al., entitled "Fruit Steam Peeler," discloses a fruit peeler system that includes a conveyor belt elevator that delivers tomatoes to a pressure steam auger wherein high pressure steam separates the skins from the tomatoes. Tomatoes then pass into a flexible cable peeler and then to a pinch roller assembly, to remove the skins from the tomatoes. The '812 patent is also incorporated herein by reference.
The capacity of a continuous, auger-type pressure steam peeler is limited by the number of tomatoes that can be exposed to steam. This is due to the decreasing percentage of surface area effectively exposed as the depth of fruit increases with increased throughput. For a given geometry and residency time, the depth of product is a function of the RPM and volume of fruit fed into the auger. Increasing throughput while keeping the fill level at its optimum level requires that the residency time be shortened. This reduces the amount of time available to heat the product and as a result, processing rates for industry standard auger-type steam peelers has been limited to throughput of approximately 20 tons/hr.
An object of the present invention is to increase capacity of auger-type steam peelers beyond present capabilities while still maintaining minimum tomato tissue loss.